6-FAMTM Fluorescein
Structure
Key data
Abmax 495 nm
Emmax 520 nm
Extinction Coef (260 nm): 20,960
Extinction Coef (at absorbance max): 75,000
5’ MW: 537.5
3’ MW: 569.5
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Spectra
With permission from IDT
Properties
6-carboxyfluorescein is a single isomer derivative of fluorescein. 6-FAM™ is the most commonly
used fluorescent dye for attachment to oligonucleotides and is compatible with most fluorescence
detection equipm ent. Below pH 7, 6-FAM™ becomes protonated, which results in decreased
fluorescence. It is typically used in the pH range 7.5-8.5. The quantum yield of fluorescein is
i
measured to 95 % at 0.1 M NaOH at 22°C with excitation at 496 nm.
Stability
Photobleaching
Under high-intensity illumination conditions, the irreversible destruction or photobleaching of
the excited fluorophore becomes the factor limiting fluorescence detectability. The multiple
photochemical reaction pathways responsible for photobleaching of fluorescein have been
ii
investigated and described in considerable details.
i
nd
J.R. Lakowicz “Principles of Fluorescence Spectroscopy, 2 Ed.”, Kluwer Academic/Plenum
Publishers, New York, London, Moscow, Dordrecht, 1999; p.53
ii
L. Song, C.A. Varma, J.W. Verhoeven. H.J. Tanke “Influence of the triplet excited state on
the photobleaching kinetics of fluorescein in microscopy.”Biophys J 1996; (70):6 2959-2968
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